In 2006, Pagliuca played a key role in the fourth-largest private-equity takeover on record, the $32 billion purchase of hospital chain HCA Inc. The deal — on which Bain Capital teamed up with KKR & Co. and Merrill Lynch — was a big win, generating a return of 5.2 times invested capital. “If HCA had gone badly, it might have been the last private-equity deal I ever did,” Pagliuca said on Tuesday. Pagliuca was on the phone — from Davos, Switzerland, where he’s attending the annual World Economic Forum — because word had just leaked out that he is retiring from Bain Capital after a 34-year run, most recently as co-chairman since 2016. Pagliuca, 68, will become a senior advisor to the firm and continue as a board member at a number of its portfolio companies. He’ll be plenty busy with the Celtics, as well as Atalanta, the Italian Serie A soccer club he bought last February. And there is his family office, a personal investing vehicle focused on biotech, tech, and space-related companies. Bain Capital will continue to be run by John Connaughton and Jonathan Lavine, who have been co-managing partners since 2016. Connaughton oversees private equity investing, while Lavine is Bain Capital’s credit investing boss. Pagliuca’s retirement was first reported by The Wall Street Journal.Bain Capital was launched in 1984 by partners at Boston management consultants Bain & Co. Their aim was to buy companies, use their management expertise to improve operations, and eventually sell at a profit. The cofounders included Mitt Romney, who went on to serve as Massachusetts governor and is now a US senator from Utah. The firm, which oversees about $160 billion in assets, has expanded beyond its private equity roots to invest in fixed-income and credit securities , venture capital, and real estate. Now one of the largest private investment firms in the world, Bain Capital has about 1,500 employees in 23 offices around the world. in 1989. He started Information Partners, a tech investment joint venture with Dun & Bradstreet, then a Bain & Co. client, that did the Gartner takeover. Many of the deals in which he’s been involved have been in the technology, media, telecommunications, and financial services sectors. One notable exception was the 2002 buyout of Burger King. The deal, done with Goldman Sachs and TPG, returned more than 5 times Bain Capital’s investment. It was an early experiment in investor-controlled doctors groups that failed amid squabbling by the medical professionals. And Pagliuca’s success in the business world didn’t necessarily carry over with voters when he sought to fill the US Senate seat in 2009 left empty by the death of Edward Kennedy. He self-funded much of a campaign that sought to position him as a pragmatic Democrat with an outsider perspective. But his candidacy, dogged by criticism over Bain Capital’s layoffs at a few of the companies the firm owned, failed to gain traction. In Davos, Pagliuca was looking to the future, not the past. He’s active on several Bain Capital deals in the works, and is looking to add more sports teams to his personal portfolio. His run at Bain Capital is coming to an end, but Pagliuca’s deal-making days are far from over. Larry Edelman can be reached at larry.edelman@globe.com. Follow him on Twitter @GlobeNewsEd.